package com.ztom.offer.v2;

import java.util.List;

/**
 * 合并两个排序的链表
 * <p>
 * https://leetcode.cn/problems/he-bing-liang-ge-pai-xu-de-lian-biao-lcof/
 *
 * @author ZhangTao
 */
public class Code23MergeTwoLists {

    public class ListNode {
        int val;
        ListNode next;

        ListNode(int x) {
            val = x;
        }
    }

    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        if (l1 == null) {
            return l2;
        }
        if (l2 == null) {
            return l1;
        }
        if (l1.val < l2.val) {
            l1.next = mergeTwoLists(l1.next, l2);
            return l1;
        } else {
            l2.next = mergeTwoLists(l1, l2.next);
            return l2;
        }
    }

    public ListNode mergeTwoLists1(ListNode l1, ListNode l2) {
        ListNode dummy = new ListNode(-1);

        ListNode cur = dummy;

        while (l1 != null && l2 != null) {
            if (l1.val < l2.val) {
                cur.next = l1;
                l1 = l1.next;
            } else {
                cur.next = l2;
                l2 = l2.next;
            }
            cur = cur.next;
        }

        cur.next = l1 == null ? l2 : l1;

        return dummy.next;
    }
}
